Iran raised its voice on Wednesday against a proposed union between Saudi Arabia and Bahrain, calling on Iranians to rally against what Tehran sees as an attempt by Riyadh to "annex" a territory formerly belonged to Iran. The Coordination Council of Islamic Dawa (propaganda), a body belongs to the Iranian regime, urged the Iranian people to protest after Friday prayers "against the U.S. plan to annex Bahrain to Saudi Arabia and express their anger against Al-Khalifa and Al-Saud regimes.

The leaders of six Gulf Arab monarchies have decided Monday to review a proposed union, which could lead to a "Sunni union" through Saudi Arabia and the tiny kingdom of Bahrain, shaken by protests by the Shiite majority, against Iran.

The Iranian government and parliament have fiercely denounced the project, saying it violated the rights of the Bahraini people and could worsen the crisis.

Riyadh and Manama have urged Tehran not to interfer in their affairs, while the Saudi Foreign Minister Saud al-Faisal Monday denounced "the threat by Iran as unacceptable and inadmissible."

The Bahraini Ministry of Foreign Affairs has reacted by saying the Iranian criticism as "undermining the independence and sovereignty" of the kingdom.

Iran supports the Shiite opposition in Bahrain which opposes the proposed union, and strongly denounced the Saudi military intervention in Bahrain in March 2011 to help the regime to suppress the popular demonstrations.

"This dangerous plot (unity) is the result of the evil American-Zionist British triangle- to prevent popular uprisings from expanding in countries of the region and to control the crisis in Bahrain where the regime of Al-Khalifa is unable to resolve, "said the Iranian Council in a statement.

The Bahrain issue is sensitive in Iran. A conservative movement within the regime still considers the island part of Iran. "The Islamic Republic, which guarantees the territorial integrity of Iran, has the right to demand the return of a separate province to the Islamic homeland", affirmed Wednesday Hossein Shariatmadari, editor of the ultraconservative Kayhan daily, who was appointed by Iran's supreme leader Ali Khamenei. "The Bahrainis themselves expressed their desire to return to Iran," he added.

These inflammatory statements and rallies planned Friday may exacerbate tensions between Iran and its Gulf Arab neighbors, exacerbated last year by a series of disputes.

Relations between Riyadh and Tehran, strained since the Saudi intervention in Bahrain, have deteriorated further after the discovery of a "conspiracy" against the Saudi ambassador in Washington blamed on Iran, as Saudi leaders also accuse Iran of fomenting disturbances among the kingdom's Shia minority.

In addition, Saudi Arabia and Qatar support the revolt against the Syrian regime – the closest ally of Tehran.